The Fluid-Structure Interaction interface has been updated and
enhanced with improved solver settings.

Geometric nonlinearity is available also in the Thermal Stress and
Joule Heating and Thermal Expansion interfaces.

Plasticity can now be added to domains selectively without
redefining the underlying elastic data.

Plasticity is now supported for orthotropic and anisotropic
materials.

Damping is available also for hyperelastic and elastoplastic
materials.

Infinite elements for truncating models covering large domains are
available.

The contact pair penalty factors have better defaults that are
available for all material models.

The contact pair can have different offset expressions for the
source and destination side boundaries.

Backward Compatibility vs. Version 3.5a

Plane Stress

Version 4 represents the out-of-plane strain as a separate degree of
freedom. Plane stress models made with version 3.5a need
to be re-solved to correctly display strains and stresses. Displacements
are correctly displayed.